Gear stage choosing apparatus, gear stage choosing method, and simulation apparatus

ABSTRACT

A gear stage choosing apparatus that chooses a gear stage of a stepped transmission of a vehicle includes a storage unit configured to store a shift map containing a relationship between vehicle speed and gear stage, a determination unit configured to determine a gear stage associated with an estimated vehicle speed after a lapse of a first period of time from current time based on the shift map, an evaluation unit configured to evaluate fuel efficiency in some gear stages, including the determined gear stage and one or more gear stages higher or lower in less than or equal to a specific number of gear steps than the determined gear stage, of multiple gear stages, and a choosing unit configured to choose a gear stage selected from among the some gear stages based on the fuel efficiency as a gear stage to which a current gear stage is changed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2019-206386 filed on Nov. 14, 2019, incorporated herein by reference inits entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a gear stage choosing apparatus for a steppedtransmission included in a vehicle, a gear stage choosing method, and asimulation apparatus.

2. Description of Related Art

In vehicles including a stepped transmission, the gear stage of thestepped transmission is automatically chosen. A gear stage is typicallychosen based on a shift map that defines in advance the relationshipbetween vehicle speed and gear stage. A shift map is defined such that,for example, fuel efficiency is optimal at an assumed standard runningload.

Kaijiang Y U, Masakazu MUKAI, and Taketoshi KAWABE, “Performance of anEco-Driving Nonlinear MPC System for a Power-Split HEV during CarFollowing”, SICE Journal of Control, Measurement, and SystemIntegration, January 2014, Vol. 7, No. 1, pp. 055-062 describes atechnique for choosing the gear stage (speed ratio) of a steppedtransmission a few seconds ahead by using a method called modelpredictive control (MPC). With this technique, a gear stage where fuelefficiency is predicted to be optimal is chosen from among all the gearstages based on the performance and statuses of an engine, a motor, agenerator, and a battery, and a running load.

SUMMARY

The running load of a vehicle fluctuates depending on the gradient of aroad surface, the condition of the road surface, the pay load of thevehicle, and the like. Therefore, a gear stage chosen as defined by theshift map does not always actually provide optimal fuel efficiency.

With the technique described in Kaijiang Y U, Masakazu MUKAI, andTaketoshi KAWABE, “Performance of an Eco-Driving Nonlinear MPC Systemfor a Power-Split HEV during Car Following”, SICE Journal of Control,Measurement, and System Integration, January 2014, Vol. 7, No. 1, pp.055-062, fuel efficiency is calculated in consideration of suchfluctuating factors; however, all the gear stages are calculated basedon a complicated model, so it is not realistic to apply the technique toreal-time control because a large amount of calculation.

Therefore, a gear stage choosing apparatus that is capable of choosing agear stage where fuel efficiency is good in a stepped transmission witha realistic amount of calculation is desired. In addition, a simulationapparatus that is capable of providing a good simulation pattern isdesired to, for example, test and evaluate such a gear stage choosingapparatus.

The present disclosure provides a gear stage choosing apparatus that iscapable of choosing a gear stage where fuel efficiency is good in astepped transmission with a realistic amount of calculation, a gearstage choosing method, and a simulation apparatus therefor.

An aspect of the disclosure relates to a gear stage choosing apparatusthat chooses a gear stage of a stepped transmission included in avehicle. The gear stage choosing apparatus includes a storage unitconfigured to store a shift map containing a relationship betweenvehicle speed and gear stage, a determination unit configured todetermine a gear stage associated with an estimated vehicle speed aftera lapse of a first period of time from current time based on the shiftmap, an evaluation unit configured to evaluate fuel efficiency in somegear stages of multiple gear stages, the some gear stages including thedetermined gear stage and one or more gear stages higher or lower inless than or equal to a specific number of gear steps than thedetermined gear stage, and a choosing unit configured to choose a gearstage selected from among the some gear stages based on the fuelefficiency as a gear stage to which a current gear stage is changed.

Another aspect of the disclosure relates to a simulation apparatus thatgenerates a gradient pattern of a running road of a vehicle and avehicle speed pattern for simulation. The simulation apparatus includesa gradient pattern generation unit configured to generate a gradientpattern of a running road by, in each of sections into which the runningroad is divided by a first distance, where a gradient obtained byincreasing or reducing a gradient of the section by a first gradient atan equal probability, sequentially deriving a gradient for each section,and a vehicle speed pattern generation unit configured to generate avehicle speed pattern by, in a model including a lead vehicle that runsin accordance with a first vehicle speed pattern, a rearmost vehiclethat runs in accordance with a first preceding vehicle followingalgorithm, and one or more intermediate vehicles that increase or reduceby one for each first period at an equal probability between the leadvehicle and the rearmost vehicle and that runs in accordance with thefirst preceding vehicle following algorithm, deriving a vehicle speed ofthe rearmost vehicle.

According to the aspects of the disclosure, a gear stage where fuelefficiency is good in the stepped transmission is chosen based on theevaluated fuel efficiency of each of some gear stages, so it is possibleto provide a gear stage choosing apparatus that is capable of choosing agear stage with a realistic amount of calculation. It is also possibleto provide a simulation apparatus that is capable of generating goodsimulation patterns of a gradient pattern and a vehicle speed patternthat are applicable to tests and evaluations for a gear stage choosingapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like signs denote likeelements, and wherein:

FIG. 1 is a functional block diagram of a gear stage choosing apparatusand its peripheral components according to a first embodiment of thedisclosure;

FIG. 2 is a flowchart of a gear stage choosing process according to thefirst embodiment;

FIG. 3 is a functional block diagram of a simulation apparatus accordingto a second embodiment of the disclosure;

FIG. 4 is a view showing an example of a gradient pattern according tothe second embodiment of the disclosure; and

FIG. 5 is a view showing a model that is used to generate a speedpattern according to the second embodiment of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS First Embodiment

Hereinafter, a first embodiment of the disclosure will be described. Agear stage choosing apparatus according to the present embodimentdetermines a gear stage based on an estimated vehicle speed and a shiftmap and chooses a gear stage where fuel efficiency resulting fromconsideration of an estimated running load is optimal from among areasonable range of gear stages including the determined gear stage andone or more gear stages higher or lower than the determined gear stageas a target gear stage (a gear stage to which a current gear stage ischanged). With this configuration, in comparison with the case where agear stage determined based on a shift map is directly chosen as atarget gear stage, fuel efficiency is improved. In addition, the gearstage choosing apparatus uses some gear stages of multiple gear stagesof the stepped transmission to evaluate fuel efficiency. Therefore, incomparison with the case where all the gear stages are used to evaluatefuel efficiency, the amount of calculation is reduced, and the gearstage choosing apparatus is suitably applied to real-time control.

Configuration

FIG. 1 shows the functional blocks of a gear stage choosing apparatus 10and its peripheral components according to the present embodiment. Avehicle includes, for example, the gear stage choosing apparatus 10, apowertrain ECU 20, a stepped transmission 21, an engine 22, a brake ECU30, a brake device 31, an EPSECU 40, an electric power steering (EPS)system 41, a driving support ECU 50, a self-driving ECU 60, a managerECU 70, a communication unit 80, and the like.

The vehicle may further include various types of devices such as anavigation system and various sensors, such as an accelerator pedalsensor, a brake pedal sensor, a steering angle sensor, a camera, anobstacle sensor that uses light or electromagnetic waves, a vehiclespeed sensor, a yaw rate sensor, and a GPS sensor. These are not shownin the drawing.

The driving support ECU 50 is an electronic control unit (ECU) that, forthe functions of collision avoidance, preceding vehicle following, lanekeeping, and the like, executes driving support control to execute partof control for the motion of the vehicle independently of a user'sdriving operation. Multiple driving support ECUs 50 may be providedaccording to functions.

The self-driving ECU 60 is an ECU that executes driving support controlto execute all the control for the motion of the vehicle independentlyof a user's driving operation. The driving support ECU 50 and theself-driving ECU 60 each are a driving controller that outputs aninstruction to control the motion of the vehicle, such as anacceleration or deceleration and a steering angle, based on informationacquired from various sensors, and the like.

The manager ECU 70 is an ECU that outputs an instruction to thepowertrain ECU 20, the brake ECU 30, the EPSECU 40, or the like(hereinafter, these are collectively referred to as actuator ECU)(described later) based on an instruction from the driving support ECU50, the self-driving ECU 60, or the like.

The manager ECU 70 is an ECU that, when the ECU receives an instructionfrom the multiple driving support ECUs 50 or the like, performs aprocess called coordination based on a predetermined rule to choose aninstruction to control the vehicle and that provides an instruction tothe actuator ECU based on the coordination result. Details of a user'smanual driving operation to a steering wheel, a brake pedal, anaccelerator pedal, or the like may be acquired by the manager ECU 70 andthen the manager ECU 70 may use the details in the coordination process,or may be acquired by the actuator ECU and then the actuator ECU mayindividually perform coordination for a user's manual driving operationand an instruction from the manager ECU 70.

The powertrain ECU 20 is an ECU that executes control to generatedriving torque or to generate braking torque caused by engine brake bycontrolling the rotation speed of the engine 22 and the steppedtransmission 21 capable of changing a speed ratio by using multiple gearstages.

The brake ECU 30 is an ECU that executes control to cause the brakedevice 31 to generate braking force.

The EPSECU 40 is an ECU that executes control to cause the EPS system 41to steer.

The communication unit 80 is capable of transmitting or receivingvarious pieces of information by wirelessly communicating with externalservers, other vehicles, and the like.

The gear stage choosing apparatus 10 is an ECU including a storage unit11, a determination unit 12, an evaluation unit 13, and a choosing unit14. The storage unit 11 stores a shift map containing the relationshipbetween vehicle speed and the gear stage of the stepped transmission 21.The determination unit 12 determines the pattern in which a current gearstage is changed to a gear stage associated with an estimated vehiclespeed after a lapse of a first period of time by consulting the shiftmap. The evaluation unit 13 evaluates fuel efficiency in some gearstages of multiple gear stages of the stepped transmission 21. Some gearstages include the determined gear stage and one or more gear stageshigher or lower in less than or equal to a specific number of gear stepsthan the determined gear stage. The choosing unit 14 chooses a targetgear stage from among the some gear stages based on the fuel efficiency.

The above-described ECUs each are typically a computer including memoryand a processor. The processor of each ECU implements a function by, forexample, reading out a program stored in non-transitory memory andrunning the program. These ECUs are connected to one another bycommunication lines and are capable of cooperatively operating bycommunicating with one another as needed.

Process

Hereinafter, the details of a process according to the presentembodiment will be described. FIG. 2 is a flowchart of a gear stagechoosing process that is executed by the gear stage choosing apparatus10. This process is, for example, started when a user turns on the power(turns on the ignition) of the vehicle to start a trip and executeduntil the user turns off the power to stop the trip.

Step S101

The determination unit 12 acquires an estimated vehicle speed and anestimated running load. An estimated vehicle speed is informationindicating a vehicle speed after a lapse of the first period of timefrom current time. An estimated running load is information indicating afactor that fluctuates the running resistance of the vehicle after alapse of the first period of time from current time and is informationdetermined based on, for example, the gradient of a running road, thetype of a road surface (such as a pavement road and a gravel road) orthe condition of a road surface (such as a wet state and a snow coverstate) indicating the slipperiness of the running load, a pay load (theweight of occupants and baggage), and the like.

The first period of time is, for example, a predetermined period of timeand is, for example, a period of time of about several seconds to 10seconds. The self-driving ECU 60 or the driving support ECU 50 of thevehicle is capable of deriving an estimated vehicle speed and anestimated running load by executing a unique process to execute each ofthe functions during operation. When the self-driving ECU 60 or thedriving support ECU 50 derives an estimated vehicle speed, thedetermination unit 12 acquires the estimated vehicle speed.Alternatively, the determination unit 12 itself may derive an estimatedvehicle speed by predicting the motion of the vehicle. The self-drivingECU 60, the driving support ECU 50, or the determination unit 12 iscapable of deriving each of an estimated vehicle speed and an estimatedrunning load based on, for example, information acquired from a pay loadsensor, a camera, an obstacle sensor, or the like of the vehicle orinformation of surrounding running roads and traffic flow acquired froma preceding vehicle or an external server via the communication unit 80.

Step S102

The determination unit 12 determines a gear stage associated with theestimated vehicle speed based on a shift map. The shift map isinformation that defines in advance a relationship between gear stageand vehicle speed. A shift map is defined for each vehicle model suchthat, for example, fuel efficiency is optimal at a running loadestimated as a standard running load. A shift map may be not onlyinformation that associates gear stage with vehicle speed but also, forexample, information that associates gear stage with a combination ofvehicle speed and the throttle opening degree of the engine 22. In thiscase, in step S101, the determination unit 12 acquires an estimatedthrottle opening degree after a lapse of the first period of timetogether with an estimated vehicle speed and determines a gear stageassociated with the estimated vehicle speed and the estimated throttleopening degree based on the shift map.

Step S103

The evaluation unit 13 evaluates fuel efficiency in each of thedetermined gear stage and one or more gear stages higher or lower inless than or equal to a specific number of gear steps than thedetermined gear stage. The evaluation unit 13 uses some gear stages ofthe multiple gear stages of the stepped transmission 21 for evaluation.Some gear stages include the gear stage determined in step S102. Forexample, one or more gear stages higher or lower in less than or equalto a number of n gear steps than the determined gear stage are used forevaluation. Here, the specific number of gear steps n is, for example, apredetermined value and may be one or two. When the determined gearstage is the lowest gear stage or the highest gear stage, the determinedgear stage and only one or more gear stages higher than the determinedgear stage or only one or more gear stages lower than the determinedgear stage are used for evaluation.

An evaluation of fuel efficiency is performed by, for example,evaluating a distance of travel per unit amount of fuel or a fuelconsumption per unit distance of travel in accordance with theefficiency characteristics of the engine 22 based on a runningresistance caused by an estimated running load, an estimated vehiclespeed, and the rotation speed of the engine 22, determined from a gearstage, loss characteristics of the stepped transmission 21 and otherdrive-train, and the like. The evaluation unit 13 evaluates fuelefficiency on each of the intended gear stages. A method of evaluatingfuel efficiency is not limited to this method, and another method may beused.

Step S104

The choosing unit 14 chooses a gear stage where fuel efficiency isoptimal as a target gear stage. A state where fuel efficiency is optimalis, for example, a state where a distance of travel per unit amount offuel is maximum or a fuel consumption per unit distance of travel isminimum.

When there are two or more gear stages where fuel efficiency is optimal,the choosing unit 14 chooses the one different in a minimum number ofgear steps from a current gear stage as a target gear stage. Thus, thenumber of times of a gearshift operation is reduced. It is less likelythat a gear stage where fuel efficiency is optimal is present on each ofhigher and lower sides of a current gear stage and those gear stages arehigher and lower in the same number of gear steps than the current gearstage. In this case, any one of the higher gear stage and the lower gearstage may be chosen as a target gear stage. A chosen gear stage may be acurrent gear stage. In other words, in the present embodiment, changinggear stages also includes keeping the same gear stage.

The choosing unit 14 provides information indicating the determined gearstage to, for example, the powertrain ECU 20 and causes the powertrainECU 20 to execute control to actually shift into the determined gearstage. After that, the process returns to step S101.

It is desirable that a process loop of step S101, step S102, step S103,and step S104 be, for example, executed at intervals of one second orlonger in consideration of a time required to change gear stages. When aprocess of choosing a gear stage based on an estimated vehicle speed andan estimated running load a few seconds ahead (first period of time) isrepeated at cycles shorter than the intervals, a gear stage where fuelefficiency is optimal is chosen with high accuracy at each point intime. An appropriate value may be selected as the first period of timeby, for example, performing a simulation.

In step S102, the range (n) of gear stages that are used for evaluationis determined as a range that includes a gear stage where fuelefficiency is optimal even under the influence of a running load. Anappropriate value may be selected as the range by, for example,performing a simulation.

In step S101, an estimated vehicle speed is a vehicle speed that isestimated when a user does not operate either the accelerator pedal orthe brake pedal. When a user is performing such an operation, thefunctions of self-driving control and driving support control arecancelled as a rule, and it may be difficult to predict a user'soperation, so the accuracy of an estimated vehicle speed is limited. Forthis reason, in this case, for example, in step S101, an estimatedvehicle speed is not acquired, step S102 and step S103 are skipped, and,in step S104, the determination unit 12 determines a gear stageassociated with a current vehicle speed based on the shift map, and thechoosing unit 14 chooses the determined gear stage as a target gearstage.

The configuration of the devices installed in the vehicle and theconfiguration and process of the gear stage choosing apparatus 10,described above, are one example, and addition, replacement,modification, and omission are possible as needed. The functions of thedevices may be implemented by integrating the devices into a singledevice or separating any one of the devices into multiple devices asneeded.

For example, the gear stage choosing apparatus 10 may be provided as anindependent ECU or may be provided so as to be distributed among thepowertrain ECU 20, the manager ECU 70, and the like. For example, thenumber of the driving support ECUs 50 is not limited, and theself-driving ECU 60 may be omitted.

Advantageous Effects

The gear stage choosing apparatus 10 according to the present embodimentdetermines a gear stage based on an estimated vehicle speed and a shiftmap and chooses a gear stage where fuel efficiency resulting fromconsideration of an estimated running load is optimal from among areasonable range of gears stages including the determined gear stage andone or more gear stages higher or lower than the determined gear stageas a target gear stage. With this configuration, in comparison with thecase where a gear stage determined based on a shift map is directlychosen as a target gear stage, fuel efficiency is improved.

In addition, the gear stage choosing apparatus 10 uses some gear stagesof multiple gear stages of the stepped transmission 21 to evaluate fuelefficiency. Therefore, in comparison with the case where all the gearstages are used to evaluate fuel efficiency, the amount of calculationis reduced, and the gear stage choosing apparatus 10 is suitably appliedto real-time control. Particularly, as the number of gear stages of thestepped transmission 21, for example, increases and is greater than orequal to four, higher advantageous effects are obtained.

When the gear stage choosing apparatus 10 acquires an estimated vehiclespeed and an estimated running load from one or more devices capable ofderiving an estimated vehicle speed and an estimated running load, as inthe case of the driving support ECU 50 or the self-driving ECU 60, theamount of calculation is further reduced.

Second Embodiment

Hereinafter, a second embodiment of the disclosure will be described. Inthe present embodiment, a simulation apparatus 100 generates a gradientpattern of a running road for a vehicle and a vehicle speed pattern for,for example, testing and evaluating the gear stage choosing apparatus 10according to the first embodiment.

Configuration

FIG. 3 shows the functional blocks of the simulation apparatus 100according to the present embodiment. The simulation apparatus 100includes a gradient pattern generation unit 101 and a vehicle speedpattern generation unit 102. The gradient pattern generation unit 101generates a gradient pattern of a running road for simulation. Thevehicle speed pattern generation unit 102 generates a vehicle speedpattern for simulation.

Process

First, a gradient pattern generation process of the gradient patterngeneration unit 101 will be described. The gradient pattern generationunit 101 sequentially derives gradients S_(i) of sections P_(i) (i=1, 2,3, . . . , N) into which a running road is divided by a first distance.Here, the first distance and the number N of sections are determined asneeded in advance according to details of tests and evaluations, and thelike. Here, a gradient is typically the ratio of a height to ahorizontal distance of a running road; however, a different definitionmay be used. A gradient may be, for example, an angle that a runningroad forms with a horizontal plane. A gradient is not limited.

The gradient pattern generation unit 101 initially sets the gradient S₁of the first section P₁ including the starting point of the running roadto a first gradient s (s>0) at a probability of ½ or to −s at aprobability of ½. Here, the first gradient s is determined as needed inadvance according to details of tests and evaluations, and the like.

The gradient pattern generation unit 101 subsequently sets the gradientS₂ of the second section P₂ next to the first section P₁ to S₁+s at aprobability of ½ or to S₁−s at a probability of ½ by using the gradientS₁ of the first section P₁ and the first gradient s.

Similarly thereafter, the gradient pattern generation unit 101 sets thegradient S_(i+1) of the (i+1)th section P_(i+1) to S_(i)+s at aprobability of ½ or to S_(i)−s at a probability of ½ by using thegradient S_(i) of the ith section P_(i) and the first gradient s, thussequentially deriving the gradient S₁ of the first section P₁ to thegradient S_(N) of the Nth section P_(N) including the endpoint.

The gradient pattern generation unit 101 outputs an array of thegradient S₁ to the gradient S_(N) derived by increasing or reducinggradients at an equal probability in this way as a gradient pattern forsimulation.

An example of the gradient pattern is shown in FIG. 4. FIG. 4 is a graphof a gradient pattern, in which the abscissa axis represents a distancefrom a starting point and the ordinate axis represents a height from thestarting point. An example of the gradient pattern is represented by thecontinuous line, and another example is represented by the dashed line.A gradient pattern generated by this method is a random pattern;however, the distribution of gradients in any section and thedistribution of average gradients of all the sections both are normaldistributions with an average of zero. Therefore, with this method,multiple gradient patterns having statistically the same property aregenerated.

Next, a vehicle speed pattern generation process of the vehicle speedpattern generation unit 102 will be described. The vehicle speed patterngeneration unit 102 uses the following model.

This model will be described with reference to FIG. 5. In this model, alead vehicle 111 runs in accordance with a first vehicle speed pattern.The first vehicle speed pattern is a predetermined vehicle speedtemporal variation pattern. The first vehicle speed pattern is notlimited. The first vehicle speed pattern may be a vehicle speed patternthat is used in the fuel consumption rate test (JC08 mode) in Japan or avehicle speed pattern that is used in Worldwide harmonized lightvehicles test procedure (WLTP) proposed as an international standard.

In this model, a rearmost vehicle 113 runs behind the lead vehicle 111.An intermediate vehicle 112 runs between the lead vehicle 111 and therearmost vehicle 113. The number of the intermediate vehicles 112increases by one at a probability of ½ or reduces by one at aprobability of ½ every first period. The first period is determined asneeded in advance according to details of tests and evaluations, and thelike. When the current number of intermediate vehicles becomes zero, thenumber of the intermediate vehicles, for example, increases by one at aprobability of ½ or remains zero at a probability of ½ in a subsequentperiod.

In the example shown in FIG. 5, in a period T1, one intermediate vehicle112 is running as an example. In the subsequent period T2, the number ofthe intermediate vehicles 112 increases by one into two as an example.In the further subsequent period T3, the number of the intermediatevehicles 112 reduces by one into one as an example. In this model, it isassumed that, for example, as shown in FIG. 5, the number of theintermediate vehicles 112 increases in a manner such that a new one cutsin just behind the lead vehicle 111 and the number of the intermediatevehicles 112 reduces in a manner such that one just ahead of therearmost vehicle 113 disappears. It is not necessary to increase orreduce the intermediate vehicles 112 in accordance with this rule. Thenumber of the intermediate vehicles 112 may increase or reduce at anylocation.

In this model, the intermediate vehicle 112 and the rearmost vehicle 113each run based on a first preceding vehicle following algorithm. Thefirst preceding vehicle following algorithm is an algorithm thatcontrols the vehicle speed of a host vehicle such that an appropriateinter-vehicle distance from a vehicle running ahead of the host vehicleis maintained. Specific details of the algorithm are not limited. Forexample, the same algorithm as the one implemented in the drivingsupport ECU 50 having a preceding vehicle following function may beemployed. The intermediate vehicle 112 and the rearmost vehicle 113 eachmay run based on a different preceding vehicle following algorithmvehicle by vehicle.

The vehicle speed pattern generation unit 102 derives the vehicle speedof the rearmost vehicle 113 in such a model and outputs the temporalvariation pattern of the vehicle speed as a vehicle speed pattern forsimulation. With this method, based on the patterns defined as standardvehicle speed patterns in JC08 mode, WLTP, and the like, multiplevehicle speed patterns incorporating realistic randomness, that is,fluctuations in the number of intermediate vehicles, are generated.

The simulation apparatus 100 may include any one of the gradient patterngeneration unit 101 and the vehicle speed pattern generation unit 102.

Advantageous Effects

The simulation apparatus 100 according to the present embodiment iscapable of suitably generating multiple variations of gradient patternshaving statistically the same property and is capable of suitablygenerating multiple variations of vehicle speed patterns incorporatingrealistic randomness into patterns defined as standard vehicle speedpatterns. For example, by applying a gradient pattern to an estimatedrunning load and applying a vehicle speed pattern to an estimatedvehicle speed, these patterns may be used to test and evaluate the gearstage choosing apparatus 10 according to the first embodiment, with theresult that promotion of development and high performance of the gearstage choosing apparatus 10 are achieved. Other than the gear stagechoosing apparatus 10, these patterns may be used to test and evaluatevarious driving support ECU 50, self-driving ECU 60, and the likeinstalled in the vehicle, with the result that promotion of developmentand high performance are achieved.

The embodiments of the disclosure are described above; however, thedisclosure may be modified as needed. The disclosure may be regarded asnot only a gear stage choosing apparatus but also a gear stage choosingmethod and a gear stage choosing program that are executed by the gearstage choosing apparatus including a processor and memory, anon-transitory computer-readable storage medium storing the gear stagechoosing program, a vehicle including the gear stage choosing apparatus,and the like. The disclosure may be regarded as not only a simulationapparatus but also a simulation method and a simulation program that areexecuted by the simulation apparatus including a processor and memory,and a non-transitory computer-readable storage medium storing thesimulation program.

The disclosure is usable in a gear stage choosing apparatus installed ina vehicle, or the like, and a simulation apparatus therefor.

What is claimed is:
 1. A gear stage choosing apparatus that chooses agear stage of a stepped transmission included in a vehicle, the gearstage choosing apparatus comprising: one or more processors programmedto function as: a storage unit configured to store a shift mapcontaining a relationship between vehicle speed and gear stage; and adetermination unit configured to determine a gear stage associated withan estimated vehicle speed after a lapse of a first period of time fromcurrent time based on the shift map; an evaluation unit configured toevaluate fuel efficiency in each of some gear stages of multiple gearstages, the each of some gear stages including the determined gear stageand one or more gear stages higher or lower in less than or equal to aspecific number of gear steps than the determined gear stage; and achoosing unit configured to choose a gear stage selected from among theeach of some gear stages based on the fuel efficiency as a gear stage towhich a current gear stage is changed.
 2. The gear stage choosingapparatus according to claim 1, wherein the choosing unit is configuredto choose a gear stage where the evaluated fuel efficiency is best amongthe each of some gear stages as a gear stage to which a current gearstage is changed.
 3. The gear stage choosing apparatus according toclaim 1, wherein, when an entire or some motion of the vehicle iscontrolled by a driving controller included in the vehicle, thedetermination unit is configured to acquire the estimated vehicle speedfrom the driving controller.
 4. The gear stage choosing apparatusaccording to claim 1, wherein the estimated vehicle speed is a vehiclespeed that is estimated when a user does not operate any of anaccelerator pedal or a brake pedal.
 5. The gear stage choosing apparatusaccording to claim 1, wherein the evaluation unit is configured toevaluate the fuel efficiency by using an estimated running load of thevehicle.
 6. The gear stage choosing apparatus according to claim 5,wherein the estimated vehicle speed and the estimated running load eachare derived based on information acquired from at least one of a sensorincluded in the vehicle, a preceding vehicle, and an external server. 7.A gear stage choosing method that is executed by a gear stage choosingapparatus that chooses a gear stage of a stepped transmission includedin a vehicle, the gear stage choosing method comprising: determining agear stage associated with an estimated vehicle speed after a lapse of afirst period of time from current time based on a prestored shift mapcontaining a relationship between vehicle speed and gear stage;evaluating fuel efficiency in each of some gear stages of multiple gearstages, the each of some gear stages including the determined gear stageand one or more gear stages higher or lower in less than or equal to aspecific number of gear steps than the determined gear stage; andchoosing a gear stage selected from among the each of some gear stagesbased on the fuel efficiency as a gear stage to which a current gearstage is changed.